1. Field of the Invention
The present invention relates to automated sealing apparatus and methods for fabricating containers adapted for sterilization. More particularly, this invention is directed to an automated apparatus for continuously heat sealing portions of moving polymer webs to form bags or tubes.
2. Description of Related Art
Packages or bags formed from gas pervious materials adapted for gas sterilization of products contained therein are known in the art. Fibrous polymer webs such as spun-bonded polyolefins and, particularly, a type of polyethylene known as TYVEK.RTM. 1059B, available from DuPont, are useful for gas and steam sterilization. Such spun-bonded polyolefins are pervious to sterilizing gases such as ethylene oxide, steam, or dry heat, while being impervious to bacteria and other contaminants.
In the packaging of surgical instruments, pharmaceutical products, and other sterile objects, sharp points or surfaces of the packaged objects may come in contact with and abrade the TYVEK.RTM. 1059B due to movement of the objects within the package during shipping or handling of the packaged product. It is advantageous to construct such gas pervious containers or breather bags from a combination of TYVEK.RTM. 1059B and other polymer webs such as polypropylene based materials which are resistant to abrasion by sharp points. It is also advantageous to construct breather bags formed from such polypropylene based materials having slits or perforations adjacent TYVEK.RTM. 1059B and lying between the TYVEK.RTM. 1059B and the packaged objects to prevent abrasion of the TYVEK.RTM. 1059B, while the slits provide access to sterilizing gas through the TYVEK.RTM. 1059B to sterilize the packaged objects.
Since TYVEK.RTM. 1059B is an opaque material, transparent polypropylene based materials in conjunction with TYVEK.RTM. 1059B are also particularly useful in constructing transparent breather bags for viewing and inspecting the contents of the package. Breather bags formed from TYVEK.RTM. 1059B and polypropylene based materials have previously been manufactured by step and seal apparatus. These step and seal apparatus intermittently move sheets of polymer materials including TYVEK.RTM. 1059B and polypropylene based materials to a staging area in incremental steps, stopping the materials at the staging area, and applying a heat sealing mechanism. Typically a heated stamp or impulse seal is used for applying heat and pressure to the materials to be heat sealed. Thereafter, the heat sealed materials are cut into individual bags while incrementally moving another set of sheets of polymer materials for heat sealing by the heated stamp.
In use, the step and seal apparatus has a typical output of 5 to 8 breather bags per minute, with the steps of stopping and sealing the polymer materials being the slowest step in production.
Continuous material sealing apparatus are known in the art. However, heretofore there has been no application of the novel features of the present invention described herein to implement continuous heat sealing of continuously fed webs of continuous polymer material, including TYVEK.RTM. 1059B, to form a continuous hermetically sealed tubular structure adapted for gas and steam sterilization, with the apparatus capable of producing 25 to 30 breather bags per minute.
The present invention increases breather bag production by implementing a continuous feeding and sealing of polymer materials, i.e. the relatively slow step and seal approach of previous breather bag machines is eliminated.